uio/uio_pci_generic: Disable bus-mastering on release (865a11f9) · Commits · 戴 / test

Userspace code using uio_pci_generic may enable bus-mastering by directly manipulating a PCI device's command register. If a userspace program enables bus-mastering but exits/crashes uncleanly, bus- mastering will still be enabled and stale DMA addresses may be programmed and live in the device. Disable bus-mastering unconditionally on last close of a UIO PCI fd to avoid this. If the device did not have bus-mastering enabled, pci_clear_master() is a no-op. Signed-off-by:

Venkatesh Srinivas <venkateshs@google.com> Reviewed-by:

Bjorn Helgaas <bhelgaas@google.com> Reviewed-by:

Catherine Sullivan <csully@google.com> Acked-by:

Michael S. Tsirkin <mst@redhat.com> Signed-off-by:

Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/uio/uio_pci_generic.c

+17 −0

Original line number	Diff line number	Diff line
		@@ -39,6 +39,22 @@ to_uio_pci_generic_dev(struct uio_info *info)
		return container_of(info, struct uio_pci_generic_dev, info);
		}

		static int release(struct uio_info info, struct inode inode)
		{
		struct uio_pci_generic_dev *gdev = to_uio_pci_generic_dev(info);

		/*
		* This driver is insecure when used with devices doing DMA, but some
		* people (mis)use it with such devices.
		* Let's at least make sure DMA isn't left enabled after the userspace
		* driver closes the fd.
		* Note that there's a non-zero chance doing this will wedge the device
		* at least until reset.
		*/
		pci_clear_master(gdev->pdev);
		return 0;
		}

		/* Interrupt handler. Read/modify/write the command register to disable
		* the interrupt. */
		static irqreturn_t irqhandler(int irq, struct uio_info *info)
		@@ -78,6 +94,7 @@ static int probe(struct pci_dev *pdev,

		gdev->info.name = "uio_pci_generic";
		gdev->info.version = DRIVER_VERSION;
		gdev->info.release = release;
		gdev->pdev = pdev;
		if (pdev->irq) {
		gdev->info.irq = pdev->irq;

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